This one is so easy however it is not one that is mentioned very often, sometimes you will need to see how a Mac performs under load, perhaps because it is crashing or overheating any reason you can think of really. Well your OSx install comes with all the CPU stress test you need.
The simple command for this is:
sudo yes
The exit command for this is just:
control C
So simple right? Now you don’t need any third party apps to test your Mac.